1. Field of the Invention
The application relates generally to methods and apparatus for attenuating and/or baffling transient pressure waves in relatively incompressible materials in organs and systems of the human body, including, but not limited to the following systems: cardiovascular, pulmonary, renal/urological, gastrointestinal, hepatic/biliary, gynecological, central nervous, musculoskeletal, otorhinolaryngical and ophthalmic.
The present application also relates generally to the fields of end-stage heart failure and noncompliant vasculature, and in particular to the treatment of disorders caused by fluctuations of intravascular pressure. In one aspect, methods and devices are provided for the treatment of hypertension and its adverse sequelae.
2. Description of the Related Art
Pressure waves are known to propagate through incompressible fluids in various organs of the body. Such pressure waves can be cyclical and part of normal body function, such as in the cardiovascular system, or more random, such as arise in response to environmental stimuli.
In the cardiovascular system, the beating of the heart cyclically pumps blood through the vasculature. This process normally generates pressure waves in the vascular system. Hypertension (high blood pressure), a malady from which many adults suffer, is associated with cardiovascular disease and stroke. Though there are many causes of hypertension, primary (or essential) hypertension is responsible for about 95% of the cases. High systolic blood pressure, i.e., the pressure in the vasculature associated with the expelling of blood from the heart into the aorta, has become the predominant concern in hypertensive patients. The determinants of systolic blood pressure are blood flow, arterial compliance, and arterial wave propagation. Aging results in arterial stiffening which decreases arterial compliance and increases systolic hypertension. As discussed further below reducing hypertension is desirable.
Pressure waves also may be caused by a number of events, e.g., events within the body, such as breathing in the lungs, peristalsis actions in the GI tract, movement of the muscles of the body, or events such as coughing, laughing, external trauma to the body, and movement of the body relative to gravity. As the elasticity of the surrounding tissues and organs, sometimes referred to as compliance, decreases, the propagation of these undesirable pressure waves increases. These undesirable pressure waves have many undesirable effects ranging from discomfort, to stress on the organs and tissue, to fluid leakage such as urinary incontinence, to renal failure, stroke, heart attack and blindness.
Pressure accumulators and wave diffusers are types of devices that can modulate pressure waves in various nonanalogous settings. Accumulator technology is well known and used in hydraulic systems in aircraft, manufacturing equipment, and water supply and distribution since the 1940s. Common types of accumulators include bladder accumulators, piston accumulators, non-separator (air over fluid), and weight loaded type accumulators.
Wave diffusers also affect the transmission of pressure waves in incompressible systems in various settings. The function of such diffusers is to interrupt the progress of a pressure wave and distribute the energy of the wave in so many directions so as to destroy the integrity of a uniform wavefront and its resultant effects. Wave diffusers may be used to protect a specified area from the impact of a wavefront.
Currently, the most common approach to treating hypertension is drug therapy. These drugs include oral medications (systemic) and drugs delivered directly into the bloodstream. These drugs may suffer from side effects, lack of effectiveness and high morbidity. Oral medications typically do not allow immediate relief of symptoms and include side effects such as dry mouth and constipation. Drugs delivered directly into the bloodstream often require continuous or intermittent catheterization for introduction of the therapeutic agents at the clinically appropriate time.
In light of the foregoing, a number of attempts have been made to combat these disorders. These attempts have included pharmaceuticals, meditation and relaxation, and neurostimulation. However, these prior art approaches do not address the reduction in dynamic compliance, e.g., in the vasculature, which results in increased blood pressure and the associated cardiovascular disorders.